Avalanche forecast

South Columbia

Mar 30 – 31, 2017Avalanche Canada
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Avalanche danger

Sat
Sun
Alpine
4 · High
Treeline
3 · Considerable
Below
3 · Considerable
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Highlights

Warming and solar induced avalanches are likely. Smaller wind slabs, storm slabs or cornice fall could "step down" and release persistent weak layers resulting in large avalanches.

Avalanche problems

  • Persistent Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Possible
    Size
    2–4
    Triggers like a cornice fall, smaller slab avalanches could trigger deep, destructive avalanches on buried weak layers. There is a low likelihood of triggering but a high consequence if triggered. These avalanches would likely run full path.

  • Storm Slabs

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Very Likely
    Size
    1–3
    New storm snow and wind have formed reactive storm slabs. Cornices are large and fragile. They may fail with daytime warming, sun exposure, or during stormy periods.

  • Loose Wet

    • Alpine
    • Treeline
    • Below treeline
    Likelihood
    Likely - Very Likely
    Size
    1–2
    Warmer temperatures and rain will deteriorate the lower elevation snowpack, initiating loose wet avalanches that may slide easily on a buried crust. If the sun shines this problem could extend high into the alpine on solar aspects.

Confidence

Moderate - Timing or intensity of solar radiation is uncertain

Weather Forecast

Drier, sunny conditions expected on Friday and then back to unsettled weather for the weekend.Friday: A mix of sun and cloud. Alpine temperatures near -2 and freezing levels 1900 m. Ridgetop winds light from the South.Saturday: Snow amounts 5-10 cm. Alpine temperatures near -23and freezing levels 1500 m. Ridgetop winds moderate -strong from the West.Sunday: Mix of sun and cloud. Alpine temperatures near -5 and freezing levels 1400 m. Ridgetop winds light with strong gusts from the West.

Avalanche Summary

On Wednesday, storm slabs proved to be reactive and ran naturally up to size 2.5 with a couple larger size 3 and 3.5. Storm slabs were also reportedly reactive to skier triggers up to size 1.5 at treeline elevations. On Friday natural avalanche activity will remain likely with the strong influence of solar radiation,  warming and wind. Fragile cornices are also suspect which are a large enough to trigger deeper slabs to release on the slopes below. If you're traveling below treeline where the avalanche hazard may be lower than it is in the alpine you still need to be diligent with your terrain use and focus on potential overhead hazards by avoiding lingering in run-out zones where large avalanches to come from above. Check out the recent Forecaster Blogs for more details.

Snowpack Summary

30-50 cm of recent storm snow has accumulated at upper elevations. The new snow is dry up high and moist from 1800 m and below. This now brings 80-120 cm of accumulated snow which overlies a rain crust below 2000 m or a sun crust on solar aspects at higher elevations. New wind slabs are developing on leeward slopes and behind terrain features and large, fragile cornices exist along ridgelines. At higher elevations, the February weak layers are down 150-190 cm and woke up during last week's storm with many avalanches stepping down to them. The deep mid-December facet layer and November rain crust both still linger near the bottom of the snowpack and a few avalanches and cornice falls have also stepped down to these layers last week resulting in some very large full depth avalanches. These layers remain a concern during this stormy period ending with warmer temperatures and sunshine. The snowpack does not adjust well to change, and these deeper weak layers should remain on your radar through the forecast period.

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